https://doi.org/10.1177/1758155919832190 Avian Biology Research 2019, Vol. 12(2) 59–66 © The Author(s) 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/1758155919832190 journals.sagepub.com/home/avb Introduction Species require various resources to enable their survival and effective reproduction. Some taxa are associated with particular types of habitat and food resources, whereas oth- ers depend on different environments and host plants or prey. 1,2 This is particularly noticeable in the case of taxa that depend on different habitats and food resources depending on the season and life stage. Usually, such spe- cies cannot survive and reproduce in areas that do not pro- vide sufficient resources or individuals, and populations that inhabit these areas have lower fitness, that is, survival and effective breeding. 3,4 However, species sometimes attempt to compensate for a deficiency of some factors in their environment using other habitats or food resources. This issue is of high importance in the light of habitat loss, fragmentation and isolation caused by anthropogenic land use. 5,6 This should be investigated, especially in rare or threatened species or those that are considered indicators, umbrellas or surrogates for some types of habitats and assemblages known to be important for conservation purposes. 7–9 Birds are known as good indicators of naturalness and biodiversity, especially in rare and threatened habitats. 10,11 Numerous bird species could be selected for studies on compensation for habitat poverty, and, among them, appro- priate indicator candidates could be designed from seden- tary taxa. Such taxa are known to be dependent on complex habitats and specialized food resources, especially those that change during the year. Moreover, these taxa can be used as keystones or surrogates, which has been demon- strated by scientific research, but they are also relatively abundant, which is a necessary factor when conducting research. Grouse (Tetraonidae) meet these criteria. 11 Among forest-dwelling grouses of Europe, two taxa have Could gaps and diverse topography compensate for habitat deficiency by the forest-dwelling bird Hazel Grouse (Tetrastes bonasia)? Marcin Matysek, 1,2 Lukasz Kajtoch, 3 Robert Gwiazda, 1 Boguslaw Binkiewicz 4 and Grzegorz Szewczyk 5 Abstract The Hazel Grouse (Tetrastes bonasia) is considered an indicator of the naturalness and heterogeneity of the forest environment. This species occurs in various woods and forages on a variety of plants. The aim of this study was to verify the hypothesis that, in Norway spruce-dominated forest stands, the Hazel Grouse compensates for habitat poverty using non-forest areas and harsh topography, which deliver food resources and shelter for the birds. We compared 14 environmental and topographic variables in forest patches occupied and unoccupied by the Hazel Grouse in the Tatra Mountains (South Poland). Multivariate modelling showed that crucial factors for Hazel Grouse occurrence in spruce-dominated high-mountain forests were southern or western exposures, the presence of streams or glades and a multilayer forest structure with lower plant species richness in the undergrowth layer. Moreover, this species avoided clearcuts and depended either on wild sites (with a high share of deadwood and treefall gaps in mature stands at higher altitudes) or juvenile stands. The results of our study confirmed that gaps in forests and diverse topography could compensate the Hazel Grouse for habitat deficiency. These findings may be important for effective protection of this species in high-mountain spruce-only dominated forests. Keywords habitat homogeneity,mountain forests, spruce, Hazel Grouse, Tatra Mountains 1 Institute of Nature Conservation, Polish Academy of Sciences, Kraków, Poland 2 Tatra National Park, Zakopane, Poland 3 Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Kraków, Poland 4 Institute of Botany, Botanical Garden, Jagiellonian University, Kraków, Poland 5 Jaslo, Poland Corresponding author: Marcin Matysek, Institute of Nature Conservation, Polish Academy of Sciences, Adama Mickiewicza 33, 31-120 Kraków, Poland. Email: matysek@iop.krakow.pl 832190AVB 0 0 10.1177/1758155919832190Avian Biology ResearchMatysek et al. research-article 2019 Article